There is limited spectrum available for satellite communications. Thus, in order to maximize the use of the available spectrum, the throughput per Hertz is maximized. The low noise temperature of the cosmos in most satellite communication (SATCOM) bands is such that, when aircraft operate at high altitudes (where atmospheric losses are low), the noise temperature of the receiver becomes dominant in determining downlink throughput for a given aperture size. In most SATCOM receiver implementations, the Low Noise Amplifier (LNA) is a significant contributor to the overall receiver noise temperature. The noise temperature of the LNA is roughly proportional to the absolute temperature of the circuitry and active devices inside the LNA package. If the circuit losses at the input to the first (front end) field effect transistor (FET) are adequately low, the first FET is dominant in determining the LNA noise temperature.
Cooling of LNAs is routinely performed in Radio Astronomy using liquid nitrogen. However liquid nitrogen cooling is not practical for most aeronautical SATCOM products. Cooling of the first FET using Peltier devices (also called Transferred Electron Devices or thermoelectric cooling devices) has been done experimentally with limited success. The excessive transfer of heat from the hot side of the Peltier device to the FET and to the cold side of the Peltier device creates problems in cooling the FET.